Hob grinding machine



May 11, 1937. E. ACKLEY 2,079,785

HOB GRINDING MACHINE Filed July 13, 1934 10 Sheets-Sheet 1 HEM y 1937. E. ACKLEY HOB GRINDING'MACHINE 1O Sheets-Sheet 2 Filed July 13, 1934 II I \llllllllllii May 11, 1937.

E. L. ACKLEY HOB GRINDING MACHINE Filed July is, 1954 10 Sheets-Sheet 4 y 1,1937. I E. L. ACK'LE Y 2,079,785

'- nos GRINDING. MACHINE Filed July-13, 1934 10 Sheets-Sheet 5 E. L. ACKLEY HOB h GRINDING MACHINE May 11, 1937.

Filed July 13, 1934 10 Sheets-She'et 7 E. L. ACKLEY HOB GRINDING MACHINE May 11', 1937.

Filed July I3, 1934 10 Sheets-Sheet 8 wnw i l 6%)? [Ac/Pie [1" WW! May-11 1937.

E. ACKLEY nos GRINDING MACHINE Filed July 13, 1934 l0 Sheets-Sheet 9 y 1937. -E. ACKLEY HOB GRINDING MACHINE Filed July 15, 1934 10 Sheets-Sheet 10 umw k Patented May 11, 1937 UNITED STATES PATENT OFFICE 2,079,785 I non GRINDING monmn Ervin L. Ackley, Worcester, Mass., assignor to John Bath & Company, Worcester, Mass., at corporation of Massachusetts Application July 13, 1934, Serial No. 735,019

'12 Claims, (01. 51-37) This invention relates to a machine for grinding hobs insuch manner that anaccurate tooth section will be preserved during the entire useful life of the hob.

To the accomplishment of this object, I have provided means by which the teeth of a hob may be ground about an offset or eccentric axis so selected that the hob when repeatedly re-sharpened at a given sharpening angle will maintain a substantially unchanged tooth section at the cutting point. I

My invention further relates to arrangements and combinations of parts which will be here-'- inafter described and more particularly pointed out in the appended claims.

Fig. 5 is a partial end view thereof, looking in the direction of the arrow 5' in Fig. 4;

Fig. 6 is an enlarged transverse sectional elevation, taken along the line 6-6 in Fig. 1; Fig. 7 is an end view of certain parts, looking in the direction of the arrow T in Fig. 1; v Fig. 8 is a view similar to Fig. 7 but showing the parts in-a different relation; I

Fig. 9 is a detail sectional view, taken along the line 9--9 in Figs. 7 and 10;

Fig. 10 is a partial left-hand end elevation of the machine; a. I

Figs. 11, 12 and 13 aredetail side views of certain parts to be described; Fig. 14 is a; diagrammatic view illustrating the method of operation of my-improved hob grinding machine;

Fig. 15 is a view similar to Fig. 14 but showing the parts in a different relation; ig. 16 is a sectionalfront elevation of the headstock and parts associated therewith;

Figs.17 to 21 are separate plan views of parts appearing in section in-Fig. 16;, 1

Fig. 22 is an enlarged front elevation of certain indexing mechanism; Fig. 23 is an end view thereof, looking in the direction of the arrow 23 in Fig. 22;

Fig'. ,24 is' a detail side elevation of certain parts, looking in the direction of the arrow 24 in Fig. 22;

line 292,9 in Fig. 28;

Y a lead screw 41 mounted in suitable fixedbearvenient manner.

Fig. '25 is-an end view of an adjusting ring or sleeve; r

Fig. 26 is a side elevation thereof;

Fig. 27 is a front elevation of a relieving slide, looking in the direction of the arrow 21 in Fig. 5 19;

Fig. 28 is a plan. view of certain knock-off mechanism;

Fig. 29 is a sectional elevation, taken along the Fig. 30 is a view similar to Fig. 29 but showing the parts in a different position; x

Fig.-/ 31 is a diagrammatic view showing the maintenance of a substantially uniform cutting angle by the use of this invention; 15

Fig. 32 is a plan view of a hob having straigh flutes; I

Fig. 33 is an end view thereof, and i Fig: 34 is a plan view of a hob having spiral General structure Referring to Fig. 1v my improved grinding ma- H chine comprises a frame 40 on which a head- 1 stock 4| (Fig. 3) is secured by bolts 42 extending through segmental slots 43. Graduations G (Fig. 25 1), may be provided on the frame 40 to cooperate with an index-line at the lower edge of the headstock 4|. By the use of the graduations and index, the headstock may be set at any desired angle for grinding tapered work. 30

A wheel carriage 45 (Fig. 1) is slidableln guideways longitudinally of the base 40 and may be provided'witha nut- 46 through which extends ings and held from axial movement therein.

The lead screw 41 is connected to a pinion 48, gear 49, pinion 50, gear 5| and pinion 52 to a shaft 53 having a handle 54 secured thereon. By turning the handle a predetermined amount after 40 each revolution of the hob is completed, the grinding wheel carriage may be adjusted axially of the hob a distance equivalent to a tooth. space.

v The grinding wheel W (Fig. 2,) is mountedon a wheel spindle 55-rotatab1e in a wheel support- 56 mounted on the. wheel carriage 45 (Fig. ,1); The grinding wheel W may be driven-by a-moto'r in the support 56 or in any other suitable or con- The general theory operationfofproved machine will;be;best understood by refer ence to Figs. 14 andgejl5. A hob His moun to rotate about an axis a, and the axis a is both movements taking place simultaneously cam shaft 64.

I link 591s pulled downward and the eccentric After during the grinding of each tooth groove in each hob land.

In Fig. 14 the parts are shown substantially at the beginning of a grinding operation on a groove in one of the lands, and the axis a is at its farthest operative distance from the axis of the wheel W. An eccentric plate 58 (Fig. 14) is connected by a link 59 to a cam lever 60 mounted on a fixed pivot 6| and having a cam follower 62 engaging a three-point cam 63 mounted on a A spring 65 holds the cam follower 62 against the cam 63, and an adjustable stop screw 66 limits upward or return movement of the eccentric plate 58.

As the cam 63 advances from the position shownin Fig. 14 to that shown in Fig. 15, the

plate 58 isturned to the position shown in Fig. 15. This shifts the axis -a about the eccentric axis b and causes the hob H to advance past the grinding wheel W to'the position shown in Fig. 15, while at 'the same time the axis a of the hob is shifted toward thegrinding wheel W position indicated in Fig. 15.

"This combined action causes the grinding wheel to grind a tooth groove along the backwardly relieved surface S of a' hob land; this land surface and the tooth groove being both concentric with the axis b of the plate 58 rather than with the axis a of the .hob.

the parts reach the position shown in Fig. 15,-further rotation of'the cam 63 allows the spring 65 to return the parts to the position shown in Fig. 14, except that return angular" movementof the hob is prevented by mechanism to be described so that the hob is relatively advanced during said return movement into position for grinding the next succeeding land.

The exceptional results attained by this eccentric grinding operation will be more fully explained after the mechanism for effecting this. result has been described in detail.

Cam driving mechanism r A The cam shaft 6% (Fig. 10) is provided with a ear 76 (Fig 8) which is connected throughchange gears ii and I2 to agear13 mounted on a shaft I (Figf 1) rotatable in a bearing in the headstock M and having a worm wheel 76- (Fig. 6) engaged by a worm TI on a worm shaft 18 also rotatable inv bearings in-theheadstock M and having a pulley I9 at its rear end connected by a belt 66 to a motor M (Fig. 1) mounted on the headstock M. The gear I3 on the shaft I5 is thus continuously rotated during the operav tion of themachine.

The change gears II and 'ITare mounted on a slotted arm 82 (Figs. 8 and 11) mounted to swing about the axis of the cam shaft 64. The arm 82 has a second and slotted arm 83 associated therewith whichis adapted to be adjustably secured by a bolt 84 (Fig. to the arm at (Fig.

12) of a toggle lever 86 (Fig.8), also mounted to swing about the axis of the cam shaft 64.

' The arm 66 is connectedby toggle links 81 and as to a fixed pivot 89. Stop screws 90 and 9| define limits of movement of the toggle link 88 in both directions. A handle 92 (Fig.8) is connected to swing with the toggle link 88, and a magnet armature 93 is pivoted at 94 on the handle '92. A spring 95 tends constantly to break the toggle.

to the A magnet 90' (Figs. 1 and 29) having pole hereinafter described.

Hob oscillating mechanism I will now describe the mechanism for supporting the hob and causing it to oscillate about an offset or eccentric axis. I

A shaft I60 (Fig. 16) is fixed in the headstock 6i and a-yoke or open frame member IIlI- (Fig. 18) is mounted to oscillate about the axis of the shaft I 06, preferably on anti-friction bearings I02 and I03. The eccentric plate 58 previously described is adjustably secured to the end of the yoke IN by bolts I06 (Fig. 10) extending through slots I05 in the plate 58. It is obvious that as the cam 63 (Fig. 10) rotates, the plate 58 and yoke I6I will be oscillated about the axis of the shaft I 00 by the action of the cam transmitted through the cam lever 60 and link 59.

The righthand end of the yoke or frame It" (Fig. 18) is provided with dove-tailed guideways IIJ'I to receive a cross slide I68 (Fig. 19). A nut III] (Figs. 16 and 18) is secured in a recess in the be provided. A .pin IIQ prevents displacement of V the block while'the machine isrunning. y

A stud H5 (Figs. 16 and 19) projects outward from one face of the cross slide I68 and is provided with anti-friction bearings H6 and III for anindex ring I26 (Figs. 16 and 21). The

index ring isprovided with ratchet'teeth IZI (Fig. 23) and at its outer end supports an arbor I22 (Fig. 16) concentric with the'rlng.

iThe hob H (Figs 1 and 16) is mounted on the arbor I22 and is held from angular movement thereon by a clamping nut I23. The offset or eccentricity of the axis of the arbor I22 relative to the axisof the fixed shaft I60 may be adjusted by turning the adjusting screw III, by which adjustment any desired ofiset relative to the axis of the shaft I60 may be obtained.

Feeding mechanism The mechanism for feeding the hob forward during the grinding operation and from one land to the next is best shown "in Figs. 23 to 27. A spring-pressed toothed plunger I86 (Fig. 23) is slidably mounted 'in abracket i3! (Fig. 22) carried byan adjusting ring I36, which in turn is rotatably mounted on the index ring IZIl-(Fig. 16)

A plurality of weighted holding pawls I (Figs. I

22and 23) are mounted on a pivot stud I36 which may be adjusted to any desired position in a segmental slot I 31 in a stand I38 secured to a portion of the headstock ti by bolts I39 extending through slots M0 in the plate. i

slide maintain a relatively fixed angular relation.

As the cross slide I08 swings in the direction of the arrow A in Fig. 23, the index ring I20pand hob H swing with the cross slide I08 and adjusting ring I34. On the return movement of the cross slide and adjusting ring, the holding pawls I35 prevent return movement of the index ring and hob, so that the plunger I30 is moved backward relative to the ratchet-teeth I2I a distance corresponding to the angular spacing of the lands on the hob H.

At each-forward swinging movement of the yoke I I cross slide I00 and adjusting ring I34, the hob H is advanced past the grinding wheel W from the position shown in Fig. 14 to the position shown in Fig. 15', and the return movement brings the next succeeding land to the position shown in Fig. 14.

Obviously the extent of oscillation will be adjusted to correspond with the angular spacing of the lands on the hob. i

Stopping device I have provided special devices for controlling the circuit of the magnet 96 and these devices are best shown in Figs. 28 to 30. A ratchet plate I42 is mounted on a stud I43 fixed in a projection I45 (Figs. 3 and 5) at the'back of the headstock M.

A cam plate I 45 (Fig. 29) is secured to one side of 2 the ratchet wheel I42 and engages a cam follower I 40 movable with a switch member I41 and mounted to swing on a fixed pivot I48.

The switch member I41 may comprise a usual mercury switch or circuit closer, connected in the control circuit of the magnet 96 (Fig. 29) A pawl I50 hangs loosely from a stud I 5I on the yoke I0l (Fig. 16). and is caused by gravity to op-- eratively engage the teeth of the ratchet wheel I 42 as the pawl is swung downward with the yoke. The upward return movement of the pawl is idle.

A shield I53 is adjustably secured to the stud I43 on which the ratchet wheel I42 is mounted and may be set in any desired fixed angular position, thus controlling the number of teeth taken by the pawl I50 at each feeding movement.

The parts are shown in Fig. 29 in inoperative or idle position, with the circuit of the magnet is interrupted.

96 broken, and with the toggle levers 81 and 88 in the position shownin Fig. 8, in which position, as previously explained, the drive for the cam 63 When it is desired to startthe machine, the handle 92 (Fig. 7) is pressed downward to bring the armature 93 against the pole pieces 91 and .98. The handle 82 is held in this position until the yoke IOI has been once oscillated, thus advancing the ratchet wheel I42 (Fig. 29) to cause the cam follower I46 to drop of! or the projection on the cam plate I45 and to move to the circuitclosing position shown in Fig. 30.

The machine will then continue in operation until the ratchet wheel I42 has made one complete revolution, bringing the cam plate I45 again to the position indicated in Fig. 29, in which position the switch I41 is opened and the magnet circuit is broken,thus stopping the rotation of the cam 63.

The shield l53 will be so adjusted that one revolution of theratchet wheel I42 will corre spond to one revolution of the index ring I and hob H. At the completion of each revolution,

riage is manually advanced axially of the hob to the next tooth groove by means of the handle 54 (Fig. 1) and connecting gearing.

If the hob'has straight flutes, as indicated in Fig. 32, the machine is then ready to be restarted and to proceed with the grinding of the next circumferential series of thread grooves.

Angular adjusting mechanism If a hob with spiral flutes is to be ground, as shown at H in Fig. 34, the hob H must be advanced angularly a slight predetermined amount after each circumferential series of thread groove isground and before the grinding of the next series is begun. The reason for this slight angular advance is clearly apparent in Fig. 34.

For the purpose of accomplishing this slight angular advance, I provide the special adjusting mechanism best shown in Figs. 22' to 27. The adjustingring I36 (Figs. and 26) is provided with worm gear teeth I60 in its lower portion, which are engaged by a worm IBI on a worm shaft I62. The worm shaft I62 is mounted in a head 1 the rotary feed stops and the grinding wheel car- I63 (Fig. 23) secured by a pivot bolt I64 to a lug I65 (Fig. 2'1) at the side of the cross slide )8. The worm shaft I62 has a worm gear I61 (Fig. 24) at its upper end, which worm gear is engaged ,by a worm I68 on a worm shaft i69 (Fig. 22)

stand-I63. A slotted plate I15 is radially adjustable at the end of the hub I12 and is provided .with "a spring plunger I16 which maybe caused to enter any desired perforation in the index disc I13. I I

Circles of perforations of difierent angular spacing are provided on the disc I13, and the I16 into radial alignment with any selected circle of perfotations.

When grinding a hob with spiral flutes, such as is shown in Fig. 34, the necessary angular advance after grinding each circumferential series. of

thread grooves will be determined on the index disc I13. After each series is completed, the plunger I16 will be advanced the requisite number of holes to give the hob H an angular advance movement corresponding to the distance 13 (Fig. 34)

An adjusting nut I18 (Fig. 22) isprovided for adjusting the worm I6I to closely meshing relaplate I15 may be adjusted to bring the plunger tion with the worm gear teeth I60 (Fig. 25) on t the lower part of the adjusting ring I34. General operation Having described the details of construction of the different parts of my, improved machine, I will now briefly indicate the general operation.

Assuming that the grinding wheel W has been 7 adjusted to the desired hob diameter and is in the position shown in Fig. l4, the machine is started by depressing the handle 92 as previously described, and the cam 63 will then move the cam lever 60 from the position shown in Fig. 14 to that. shown in Fig. 15. This swings the eccentric plate I 1 58 and produces both an angular advance feed of the hob H aboutits own axis and also a simultaneous movement of said axis from the position shown at a in Fig. 14 to that shown at a in Fig. 15.

The grinding wheel W is thus caused to grind a thread groove in the face of the land, which face is concentric with the axis b (Figs. 14 and 15.) corresponding to the center of the fixed shaft on (Fig. 16).

grooves are ground in a radial plane in all of the lands of the hob, whereupon the magnet circuit is broken by the switch mechanism shown in Figs. 28 to 30 and the machineis brought to rest. "By thus grinding a hob with the teethmoving about an eccentric axis, I am able to produce a hob which may be repeatedly ground at a constant sharpening 'angle without "perceptibly changing the tooth section. This characteristic is made plain in the enlarged diagrammatic view (Fig. 31) in which the lines X, X" and X indicate cutting faces produced by sharpening in successive planes each passing through the axis a of the hob.

The lines Y, Y and Y indicate corresponding lines drawn through the point b about which the tooth grooves of the land were ground as indicated in Figs. l4and 15. The anglem between the pairs of lines X-Y, X'-'-Y, and X -W will -be seento be'substantially constant throughout the entire cutting width of the land. 7

I thus produce a hob which may be repeatedly reground without perceptible change in tooth section and which may accordingly be thus reground until the entire working surface of the hob has been fully utilized. The hobs may have either straight or spiral lands and the machine may be adapted to the production of tapered hobs by angular adjustment of the headstock.

1 If repeated grinding cuts in the same thread groove are desired, the holding pawls i35 may be disabled, thus preventing forward feed at the end of the cut.

The machine may also be used with a wide-face wheel for surface grinding of the lands.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:

. 1. A hob grinding machine comprising a grinding wheel, a supporting member-for a hob, a ratchet wheel on said supporting member, means to relatively adjust said wheel and hob axially,

said supporting member being mounted to swing about a \fixed axis eccentric to the axis of said hob but parallel thereto, means to oscillate said supporting member about said fixed axis, and

relatively fixed pawl means engaged by said.

to relatively adjust said wheel and hob axially,

said supporting member being mounted to swing about a fixed axis eccentric to the axis of said and relative to said wheel, said wheel operating on said hob during the oscillating advance movement in one direction only, means to maintain a fixed angular relation between said hob and sup-' porting member-during each oscillating advance movement in said direction, and means to shift said hob angularly relative to said supporting member during each return swing of said supporting member and hob and while said grinding wheel is out of engagement with said hob.

.3. A non grinding machine comprising a grind,-

ing wheel, a supporting member for a hob, means to relatively adjust said wheel and hob axially,

means to oscillate said hob and supporting member about an axis eccentric to the axis of said hob but parallel thereto and within the periphery of the supporting member, means to hold said hob in fixed angular relation to said supporting member only during the advance swing thereof and during the grinding coaction of said wheel and hob, and a feeding device rendered operative by the return swing of said supporting member to angularly shift the hob relative to said member, said shifting movement taking place entirely during said return swing.

4. In a hob grinding machine, means to simultaneously grind and relieve a thread groove in a hob, means to advance said hob angularly relative to said grinding wheel, automatic means to stop the grinding operation at the completion of each single revolution of the hob and at the simultaneous completion of each circumferential series of thread grooves in said hob, and means to adjust said automatic stopping mechanismto correspond to the number of lands in said hob.

5. In a hob grinding machine, means to simultaneously grind and relieve a thread groove in a hob, means to advance said hob angularly relative .to said grinding wheel, a continuously rotating driving shaft, a magnet to hold said hob-advancing means in operative relation to said driving shaft, and a stopping device efiective to break saidmagnet circuit when a circumferential series of thread grooves is completed.

6. A hob grinding machine comprising a grinding wheel, a supporting member for a hob, means to relatively adjust said wheel andhob axially,

said supporting member being mounted to swing about-a fixed axis, a cross slide on said supporting member, means to rotatably support a hob on said cross slide, means to radially adjust said cross slide on said supporting member, means to oscillate said supporting member, and means to feed said hob a predetermined angular amount during each return movement of said supporting member.

7. The o'mbination in a hob grinding machine as set forth in claim 6, in which additional manual means is provided for angularly advancing said hob relative to said cross slide and support.

8. The combination in a hob grinding machine as set forth in claim 6, in which an additional indexing device is mounted on said cross slide and is manually operable to advance said hob relative .to said cross slide and supporting member.

9. The combination in'a, hob grinding machine as set forth in claim 6, in which additional manual means is provided for angularly advanc- Q ing said hob relative to said cross slide and sup-' port, said latter means including an index plate headstock angularly adjustable on said frame, a

and a 'radially adjustable arm having a plunger I i grinding wheel, means to adjust grinding' wheel axially, a shaft fixed in said headstock, a

yoke mounted to swing on said shaft, means tof'7 oscillate said yoke with a predetermined swing, a cross slide mounted for radial adjustment on said yoke, a stud on said cross slide, a hob support rotatably mounted on said stud, means to cause said hob support to swing with said cross slide during a grinding operation, and meansto give said hob support a feeding movement relative to said cross slide during each return swing of said hob support. Y

11. The'combination in a hob grinding machine as set forth in claim 10, in which additional-means is provided for angularly adjusting the means which swings said hob support, the adjustment being relative to said crbss slide and of a pre- 15 determined slight amount which will compensate for the angular advance of a spiral land.

12. A hob grinding machine comprising a grinding wheel, a supporting member for a hob, means to relatively adjust said wheel and hobaxially, mean to oscillate said hob andsupporting member 'aboutan axis eccentric to the axis of said'hob but parallel thereto, and means to'maintain a fixed angular relation between said hob and supporting member during the grinding operation on each tooth of the hob, said oscillating means comprising a continuously rotating cam, a cam lever swinging about a fixed pivot and connected to said supporting member, a cam' follower on said lever, and adjusting means to limit the return movement of said cam lever.-

nnvmn ACKLEY. 

